Keeps your partner from helping you when you're in trouble (single player only).

AR Ammo Pickup Incr.

8000

Increases 5.56 NATO ammo pickup amount.

Shotgun Shell Pickup Incr.

8000

Increases 10 & 12-gauge shotgun shells pickup amount.

Magnum Ammo Pickup Incr.

25000

Increases .50 Action-Express and .500 S&W Magnum ammo pickup amount.

Rifle Ammo Pickup Incr.

8000

Increases 7.62 NATO and 12.7mm ammo pickup amount.

Grenade Pickup Increase

22000

Increases 40mm explosive, avid, and nitrogen rounds pickup amount.

Arrow Pickup Increase

20000

Increases normal and pipe bomb arrows pickup amount.

Grenade Power-Up

40000

Grenades deal 100% additional damage.

Handgun Master

37000

Handguns deal 100% additional damage.

Shotgun Master

38000

Shotguns deal 100% additional damage.

Magnum Master

40000

Magnums deal 100% additional damage.

Sniper Master

39000

Sniper Rifles deal 100% additional damage.

Machine Pistol Master

38000

MP-AF & AB 50 deal 100% additional damage.

Assault Rifle Master

37000

Assault Rifles deal 100% additional damage.

Grenade Launcher Master

40000

Gren. Launcher deals 100% additional damage.

Crossbow Master

40000

Crossbow deals 100% additional damage.

Infinite Handgun

79000

Infinite ammo for Handguns.

Infinite Shotgun

89000

Infinite ammo for Shotguns.

Infinite Magnum

99000

Infinite ammo for Magnums.

Infinite Sniper Rifle

79000

Infinite ammo for Sniper Rifles.

Infinite Machine Pistol

89000

Infinite ammo for Machine Pistols.

Infinite Assault Rifle

89000

Infinite ammo for Assault Rifles.

Infinite Grenade Launcher

99000

Infinite ammo for Grenade Launchers.

Infinite Crossbow

79000

Infinite ammo for the Crossbow.

Unlocking Skills

For leveled skills you simply need to unlock the previous level first in order to purchase the next one.

For the J'avo Killer Lv.1 and Zombie Killer Lv. 1 you'll need to kill 30 of each of those enemies first to unlock the skills.

For the master/power-up' skills (which increase the damage of a particular weapon type by an extra 100%), you'll need to kill a large amount of enemies with that weapon type. The amounts are as follows:

Weapon Type

Kill Requirement

Grenades:

800 Kills

Handguns:

1500 Kills

Shotguns:

1000 Kills

Magnums:

800 Kills

Sniper Rifles:

1000 Kills

Machine Pistols:

1500 Kills

Assault Rifles:

1500 Kills

Grenade Launchers:

1500 Kills

Crossbow:

800 Kills

In order to unlock the 'infinite ammo' skills series - that is, make themavailable for puchase - you'll need to unlock all four campaigns (including Ada's) first. You can then purchase any of these handy skills.

For your convenience, here are all weapons for each type (where applicable):